Influenza is one of acute and viral respiratory infectious diseases which are seriously harmful to human health. Since the 21st century, the prevalence of SARS, virus H5N1 and influenza virus type A H1N1 bring great harms to human beings. At present, there are still no natural drugs capable of effectively treating viral influenza and pneumonia in the world.
Fructus Forsythiae is dried fruits of Forsythia suspensa (Thunb.) Vahl (Oleaceae), which is mainly grown in Henan, Shanxi, Shanxi, Shandong provinces and other places in China, as well as Hubei, Hebei, Sichuan and Gansu provinces. Forsythiae is commonly used for treating diseases of acute wind-heat common cold, carbuncle and sore, tuberculous lymphadenitis, urinary tract infection, etc. The major components of Forsythia suspensa include phillyrin and phillyrin aglycone (also known as phillygeninin), and the structure of the two components are represented by the following formulae.

Phillyrin, as a major component of Forsythia suspensa, has antiviral, antibacterial, antioxidant, free radical scavenging and other pharmacological effects. Phillygeninin, also known as a major active component of Forsythia suspensa, has antioxidant, blood lipid lowering, free radical scavenging, bacteriostasis, anti-tumor and anti-inflammatory effects. The published literatures were mainly directed to study on the antiviral pharmacological effects of Forsythia suspensa extracts containing unknown components and several known components, and phillyrin single component. However, the antiviral pharmacological effects of the phillygeninin/phillyrin composition and the phillygeninin single component were not studied yet.